long bbl shooter
 

I have this 12" .30 luger mismatched shooter that I am having problems with getting to cycle the action when firing. I am using conventional factory loads and have weakened both the main recoil spring and firing pin spring. It still doesn't function. Is my only recourse to land load a stronger cartridge? The gun does not have the carbine recoil spring.

http://forum.lugerforum.com/lfupload/long_bbl_copy1.jpg

I was able to get a 9mm 16inch barrel function by shorting the recoil spring and using a 147 grain round. I did nothing to the firing pin spring. I started with a .30 Luger commercial pistol. Can you get heavier rounds for the .30 Luger?

I believe the reason the carbines had the extra spring in the forearm is because due to the extra mass of the bbl and forearm (in your case the extra weight of the bbl), the recoil spring has to be so weak for full retraction that it isn't strong enough to pick up another cartridge from the magazine and close the action. You can try a lighter recoil spring & handloads with a heavier bullet to give it more recoil, but I'm not sure this will solve your problem.

Hugh, I have never understood this. The toggle action works by itself, why would a heavier barrel cause it not to recoil properly?

Also, I thought the longer barrel would increase the velocity (at least a bit), causing more rearward "push".

I do not claim to be any sort of science whiz, so small words please, ;)

Ed

Ed,
The toggle action does not work by itself. In essence, it is thrown backwards by the speed of the barrel/receiver in recoil. As the barrel/receiver moves to the rear, the toggle knobs strike the frame "ears" and move upward unlocking the toggle links allowing the breechblock to move independently of the receiver. The lug on the bottom of the receiver stops the rearward motion of the barrel/receiver but the speed of the movement to the rear gives the toggle train the inertia to continue its rearward motion.

The longer barrel may give the bullet a bit more velocity, but it is only a small increase. The barrel on this Luger is huge in comparison to the standard barrel or even a carbine barrel. Not to get too technical, force is equal to the mass of an object times its velocity. You have a very small mass (the bullet) times a small increase in velocity. This is nowhere near enough inertia (force) to overcome the greatly increased mass of the heavy barrel. Given one of Newton's laws that for every action there is an equal and opposite reaction, the heavy barrel has upset the balance required to cause the action to function properly.

The force imparted to the barrel/receiver by the bullet (action) is only marginally improved by the increased velocity derived from the longer barrel length. But the mass of the barrel/receiver is greatly increased by the heavy barrel thereby reducing the effect of this small force. So the rearward motion (velocity) of the barrel/receiver (reaction) is proporionally reduced. This slowing down of the rearward motion results in the failure of the action to cycle properly. That is why the original carbine rounds were loaded "hotter" and the forearm had an accelerator spring to help return the action to battery. The 1920 carbines eliminated the accelerator spring by employing a heavier mainspring, but it still required a heavier load and the barrel was considerably lighter than the bull barrel on this gun. Weakening the spring will let the barrel/reciver group move to the rear faster, true, but then there isn't enough spring "energy" to return the action to battery.

Bottom line is that unless magnum loads with a heavy spring are used, it isn't going to cycle properly. The firing pin spring has virtually no effect.

thanks, that is 'about" what I thought....



ed

Yeah!! What Ron said... sheesh Ed, don't you know nothin'?:p


Just a note: Velocity is increased approximately 25 FPS + or - per additional inch of barrel length.

Thanks, Ron, very well explained!:cheers:

Rick, the muzzle dimension of the 12" bbl measure 0.57" and I have not considered modifying the contour. I am used to shooting 90gr jacketted bullets with 4.5gr of unique in my 7" shooter. I am going to load a few cartridges at 5gr of unique and try that with the long bbl. I'm not sure how high of a load I can go with .30 luger and a 90gr jacketted slug. thanks for the comments.